1. Field of the Invention
The present invention relates to a disk drive unit.
2. Description of Prior Art
Hitherto, there have been various equipment for recording/reproducing data by irradiating laser light to a recording medium such as a disk.
For instance, as such optical disk recording media, there have been developed a CD (compact disk) type disk and a disk called DVD (Digital versatile Disk/Digital Video Disk) suitably used for multi-media. A recording apparatus accommodating to those optical disks irradiates laser light modulated by recording data to tracks on the disk to record the data by a phase-change recording method for example.
Because the DVD itself is handled in a naked manner for example, however, there is a possibility that the surface of the disk collects dust or is scratched as the user uses the disk. Such dust and scratch (those on the surface of the disk such as dust and scratch will be called as contaminant as a whole hereinafter) become a factor of blocking the laser light. When the laser light is blocked by the contaminant on the surface of the disk as described above, a quantity of light arriving to the recording plane drops, thus causing a case when data cannot be recorded correctly.
Further, a quantity of light reflected from the disk changes due to the contaminant or defect caused on the recording plane during the disk manufacturing process. Accordingly, it becomes difficult to execute focus servo control and tracking servo control stably because it is unable to obtain normal focus error signals, tracking error signals and the like.
Then, the normal recording condition has been obtained by detecting such defect for example based on the changes of the quantity of light reflected from the disk and by holding the servo signal or by stopping the recording operation once to retry for example based on the result of detection.
However, the recording operation of a disk drive unit has been carried out by storing storage data supplied from an external equipment such as a host computer once in a buffer memory provided within the disk drive unit for example and by reading the recording data stored in the buffer memory. That is, when a number of times of retry increases, the frequency of reading recording data from the buffer memory drops. Accordingly, particularly when image data (video data) supplied continuously in correspondence to real time is to be recorded, an amount of data to be read out drops with respect to an amount of data read in, the storage area of the buffer memory saturates and some data may be lost. That is, there has been a problem that the number of times of retry increases and it may become difficult to carry out the recording operation stably as contaminant increases on the surface of the disk.
In order to solve such problems, according to the invention, a disk drive unit comprises head means for irradiating laser light to a loaded disk recording medium via an objective lens so as to at least recording data; objective lens driving mechanism for moving the objective lens in the direction of contacting/separating to/from the disk recording medium and in the radial direction of the disk recording medium based on certain control signals; reflected light quantity detecting means for detecting a quantity of reflected light of beam irradiated to the disk recording medium; light quantity reduction speed discriminating means for discriminating whether the reduction speed of the quantity of light detected by the reflected light quantity detecting means is faster than a certain time constant or not; and laser light output control means for controlling an output level of the laser light based on the discrimination result of the light quantity reduction speed discriminating means.
A disk drive unit also comprises head means for irradiating laser light to a loaded disk recording medium via an objective lens so as to at least recording data; output light quantity detecting means for detecting a quantity of output light of laser light outputted from the objective lens; reflected light quantity detecting means for detecting a quantity of reflected light of beam irradiated to the disk recording medium; and output light quantity control means for controlling an output level of the quantity of output light so that a product of the quantity of output light and the quantity of reflected light becomes a predetermined value.
The invention allows the cause of changes of a quantity of reflected light to be discriminated based on speed of the changes of quantity of reflected light from the disk recording medium. It then allows a required control corresponding to the change of quantity of reflected light to be made.
It is also possible to maintain a quantity of laser light arriving at the recording plane of the disk recording medium by keeping the product of the laser light and the reflected light from the disk recording medium constant.